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The basics about headphones: How does sound amplification work?

The basics about headphones: How does sound amplification work?

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In today's chapter, continuing the series "The basics over headphones", we will talk about amplification! What does amplification help our headphones to play as intended? For that we have to first understand how it works within a headset system.

The basics about headphones: How does sound amplification work?Photo: Flvio Sganzerla

What is a headphone amplifier?

The amplifier (amp) is responsible for amplifying the analogue electrical signal provided by the DAC after conversion (read here and understand how a DAC works). Without the amp, a DAC alone would not be able to make a phone ring. Therefore, all the devices we use to play (smartphone, notebook, desktop, etc.), must have an amplification section.

When an integrated or dedicated amplifier?

An amplifier can be integrated into the source (read here and understand what a source is), as in a smartphone, or separately, where it is already considered a dedicated amplifier.

When the amplifier is integrated in equipment classified as portable, in most cases we have an amplification section with low power output. This is because in its development it was thought to be used in conjunction with easy to push headphones, which do not have much need for "strength". This type of amp has been designed for portable headphones such as in-ears and on ears / supra aural (learn more about the types of headphones here), so don't wait too long when you are going to plug in a headphone with high impedance and low sensitivity in the your cell phone (of course there are exceptions to the rule, but I'm talking about most).

When a dedicated amplifier, the thing already changes shape. Here we are talking about a dedicated amplification board, so we will have higher quality components and at the same time a greater output power. To the detriment of this, although some headphones don't really need dedicated amplification, they benefit from it because of its quality. A dedicated amp can be portable (with battery) or desktop (powered by a source connected to the outlet).

Amplifier technologies (types)

  • Solid state amplifier (SS or Solid State) or transistorized amplifier
  • Tube amp (tube amp)
  • Hybrid (SS part and valve part)
  • Amplifier for electrostatic headsets (Electrostatic Headphone Amplifier)

The need for transformers in Solid State (SS) and Tube amplifiers

A solid state amplifier uses a combination of transistors to operate. The tube amplifier, in turn, uses vacuum tubes (valves) to amplify the signal.

Amp WooAudio - Photo Augusto SchweickardtAmp WooAudio – Photo Augusto Schweickardt

The biggest difference between a Solid State amplifier and a tube amplifier is that, while a current-driven solid state amp in all output devices (solid state circuits), a voltage-driven tube amplifier is applied to the valves.

The need for transformers in amplifiers

Voltage alone cannot move a speakerphone, which is why you need output transformers. You will notice that most tube amps have three large, heavy objects, usually at the rear. One is the power transformer and the other two are output transformers (one for each channel) that convert the output voltage of the tubes (valves) into current in the SE (Single End) and / or balanced output (s) (know what Single End output is balanced here)

AMP Solid State - Photo: Joo PauloAMP Solid State – Photo: Joo Paulo

A solid state amplifier usually has a single power transformer and no output transformer, since the tube amps need a high voltage for the valves and since they have a high output impedance, they require a transformer. Transformers are the most expensive components in any amplifier. When eliminating a transformer, Solid State (SS) amps obtain a huge cost advantage when compared to tubes. This makes it difficult to find cheap tube amplifiers.

Temperature difference between a Solid State (SS) amplifier and a Tube

Another difference between an SS amp and a tube amp at operating temperature. The valves generally heat up much more than a circuit board in a Solid State amp.

Construction of a hybrid amplifier

The intention of designing a hybrid amplifier is to combine the best attributes of the SS and Tube amplifiers. The valves generally offer more analogue, organic reproduction while the transistorized circuits offer the ability to push difficult headphones providing dynamic and authoritative sound. Of course, the sound characteristics mentioned here can vary a lot, there is always an exception to the rule, as it depends on several factors in the construction of the amplifier.

In the hybrid amplifier, the sweet mediums, the size of the sound stage, the air and the overall musicality of the valve entry section pass directly to a low-state Solid State output stage that retains much of the good qualities of the valves, providing a best interface for modern headphones.

Sound differences between a Solid State and Tube amp

Within the headset hobby group, there are audio enthusiasts and musicians who really care about their sound, there are people who think the tubes sound better and those who think the solid state amps are as good as they are better. Enthusiasts who like Solid State can provide highly technical data to support their arguments, as well as those who like Valves.

There are actually two subgroups when it comes to amplifiers. Those amplifiers that are designed to create music and those that are designed to reproduce music. Musicians want amplifiers that can deliver a wide sound, from clean to distorted and harmonic. Audio enthusiasts want amplifiers that reproduce music in the most original way possible, they don't want to create distortions, they want to reproduce the distortion made by others in music.

Distoro is one of the main selling points for lovers of tube amplifiers. Solid state amplifiers do not seem to distort as musically as vacuum tube designs. The main reason is that when you take the valves to their maximum, demanding too much of them, the distortion gradually appears and presents itself as a gradual compression that turns into distortion.

Solid State amplifiers use low voltage supply rails to operate and thus cause the output to exceed the supply voltage. When that happens, they don't start to compress and cut gradually. They simply cut the exit signal at that level. The sine waves immediately become square waves and the sound is not pleasant. Distortion of solid state amps in their pure form sounds something like bees in a bag. But that does not mean that all amplifiers will necessarily suffer from this disease, there are projects and projects where this inconvenience is minimized to the maximum.

But there is one thing that musicians and audiophiles alike love in the sound of the tubes, their uniform harmonic distortion. The harmonic distortion of the valves fills the sound and adds warmth.

We must also consider the ease with which a user can change the sound of his amplifier. When it comes to modification, there is nothing better than a tube amp. As the tubes are fitted, they can be easily removed and replaced by users. You begin to enter a new world, the world of tubes and their diversity of sounds and prices. The endless search for a tube that sounds different or better than the one you used before.

Now, if you want to modify the sound of a solid state amplifier, you need to open it. The circuits of the Solid State amps are more complex and consequently the tendency to "shit" is greater than in a tube amp. Static electricity, for example, can burn components of the amp, as well as the heat of an improperly used soldering iron. If you want to adjust a solid state amp, you need qualified technology for that. The tubes fit into a socket only one way, while the solid state components are easy to install improperly if you don't know what you're doing. Of course, it is not something out of this world, but to do any procedure it is ideal to research a lot or to know someone who has already made such a modification in a specific amplifier model.

Amplifier for electrostatic headphones

They are amplifiers that need a voltage to work and were made only / exclusively for electrostatic headphones (an article dedicated to the technologies of the headphones will be written soon). We will have a chapter dedicated to headphones and electrostatic amplifiers, so wait.


Anyway, the amplifier is a component that makes a good difference in the sound of a headset, if you really need amplification. It can also provide a good complement to the sound in case the phone has medium resistance or good sensitivity for example.

Analyzing the headset system as a whole (source, amplifier and transducer), the amplifier brings more difference in the final sound quality compared to the source. However, the part that will make the biggest difference, in the entire chain, remains the headset. However, if you already have a good phone, I think it's time to buy your amp and enjoy the music even more!

This article made in partnership with the Headphones High-End Group: